Most microorganisms present in nature are known to utilize O-succinylhomoserine or O-acetylhomoserine as an intermediate for the biosynthesis of methionine. Generally, O-succinylhomoserine is produced by homoserine O-succinyltransferase (MetA) which conjugates the succinyl group of succinyl-coA to homoserine, and O-acetylhomoserine is produced by homoserine O-acetyltransferase (MetX) which conjugates acetyl group of acetyl-coA to homoserine. That is, in producing O-succinylhomoserine among intermediates, metA is one of the most important genes in the development of microorganisms producing the same. Meanwhile, unlike MetA, MetX is known to be not feedback inhibited and have high enzyme stability.
O-succinylhomoserine can be produced using a strain with a deletion of metB gene encoding cystathionine gamma synthase in the methionine biosynthesis pathway. However, the O-succinylhomoserine-producing strain requires L-methionine. For this reason, the activity of homoserine O-succinyltransferase is inhibited by being subjected to feedback inhibition by the methionine added to the medium, and eventually, O-succinylhomoserine cannot be obtained at high concentration.
Accordingly, many prior patents have focused their studies on the release of feedback inhibition of metA from a feedback control system. However, the homoserine O-succinyltransferase encoded by metA has problems in that the wild type protein itself has low stability and that the introduction of a mutation for the release of feedback inhibition aggravates the instability. Accordingly, for the development of an O-succinylhomoserine-producing strain with high productivity, it is necessary that the feedback inhibition of the metA gene be removed and the enzyme stability be secured.